The invention discloses a high-efficiency plugging oil-base drilling fluid and a preparation method thereof. The drilling fluid is prepared from the following raw materials in parts by mass: 70-80 parts of slurrying oil, 20-30 parts of slurrying water, 2.5-3.0 parts of main emulsifier, 1.5-2.0 parts of auxiliary emulsifier, 2.0-2.5 parts of wetting agent, 2.0-2.5 parts of flow pattern regulator, 2.5-3.0 parts of fluid loss agent, 1.5-2.0 parts of alkalinity regulator, 0.5-0.8 part of extracting agent and 7-9 parts of plugging material. A weighting material is added so that the density of the drilling fluid reaches 1.45-1.56 g/cm<3>. By utilizing the well-drilling positive differential pressure, the high-efficiency plugging oil-base drilling fluid quickly implements bridging, filling and filming to plug the formation fractures on the well wall surface and near the well wall, effectively prevents the drilling fluid and filtrate thereof from permeating into microfractures, enhances the bearing capacity of the formation, has favorable plugging effect, and is beneficial to the stability of the well wall.